In the design of aircraft, it is desirable to operate the aircraft accessories with a constant frequency source of electric power. In some conventional systems, an integrated drive generator is used, powered by the aircraft engine. The generator or alternator provided for this purpose must therefore be driven at a constant speed. As aircraft engines usually have a wide speed range to accommodate the varying power requirements of take-off, landing and flight, a constant speed drive transmission driven by the engine and driving the generator or alternator must be provided to maintain a stable source of electric power for the aircraft's accessories. Various parameters are considered in designing such a constant speed transmission, such as the confined envelope or space into which the constant speed transmission is mounted between the engine and the generator or alternator, and the transmission must be capable of delivering considerable power to the alternator under varying environmental conditions and over a wide range of input speeds. Examples of such integrated drive generators are shown in U.S. Pat. Nos. 3,365,981 to Gantzer, dated Jan. 30, 1968, and 4,252,035 to Cordner et al, dated Feb. 24, 1981, both assigned to the assignee of the instant invention.
Such integrated drive generators as described above include a casing with an input shaft extending into the casing to drive the components of the generator. Coolant or oil is used for cooling and lubricating the various components of the generator. One of the major problems with integrated drive generator systems of the character described above, is the maintenance of a desired level of oil or coolant in the system. Normally, oil flows through the entire aircraft engine system, including the integrated drive generator, and it often is difficult to monitor and control the oil level. Oil from other portions of the system can even drain into the integrated drive generator, or the generator casing itself may become "starved" while other areas of the system have adequate or more than adequate oil or coolant. It is important to maintain a proper level of oil in the integrated drive generator in order to prevent the oil from migrating into the generator "gap" between the windings. In addition, it is desirable to maintain the oil level in the integrated drive generator as low as possible, while still maintaining adequate lubrication and cooling, because any build-up of the oil level may interfere with the high speed operation of the generator parts. Furthermore, the monitoring and control system must be substantially immune to attitudes and "G-levels" of the aircraft during maneuvers. Therefore, the invention is directed to a fluid or oil/coolant monitoring and control system located in the integrated drive generator where an appropriate casing and other moving part can provide an excellent monitoring station, whereas other components or areas of the aircraft system may only have coolant flow therethrough.
This invention is directed to an improved air/oil management system incorporated directly into the integrated drive generator system used in an aircraft electrical generating arrangement.